As described in related patent applications, a linear wet-deposition system has been developed to deposit fluids (e.g., water-based or solvent-based) onto a single semiconductor wafer with a pair of proximity heads located above and below the wafer. In particular implementations of the system, the proximity heads facilitate the formation and maintenance of a fluid meniscus or film on a semiconductor wafer. See e.g., U.S. application Ser. No. 11/820,590 entitled “System, Method and Apparatus for Maintaining Separation of Liquids in a Controlled Meniscus” filed on Jun. 19, 2007, which is hereby incorporated by reference.
In some instances, a proximity head in a linear wet system is configured to deposit material in only one phase, namely, liquid (e.g., water, deionized water, water-based chemistries, or solvent-based chemistries); that is to say, the deposited fluid should be devoid of material in a gas phase. However, during operation of such a system, air bubbles (e.g., material in a gas phase) can become trapped in the proximity head located above the wafer and then can accumulate on the surface of a wafer, which tends to be both hydrophobic and oleophobic. These bubbles represent a volume on the wafer surface where uniform deposition of the fluid cannot occur.
Consequently, there is a need for a wet-deposition system which does not allow the accumulation of air bubbles when depositing an air-free fluid onto a semiconductor wafer with a proximity head located above the semiconductor wafer. However, the invention claimed below has wide applicability to other applications beyond this particular application, as will become apparent from the following description and the drawings which accompany it.